1. Field of the Invention
The present invention relates to a titanium-silicalite molecular sieve and a method for preparing the same, and more particular to, a titanium-silicalite molecular sieve having a transition metal and a method for preparing the same.
2. Description of the Prior Art
Crystalline titanium-silicalite molecular sieves are formed by incorporating titanium into the zeolite structure of silicon dioxide. TS-1 molecular sieves have the MFI structures, and TS-2 molecular sieves have the MEL structures. These molecular sieves are used in oxidation reactions such as ammoximation of cyclohexanone and hydroxylation of phenol which use hydrogen peroxide as the oxidant.
Cyclohexanone oxime is the intermediate of the preparation of amides. U.S. Pat. Nos. 4,968,842, 522,752, 5,312,987 and 6,828,459 disclose using cyclohexanone, ammonia and hydrogen peroxide to form cyclohexanone oxime. However, in such methods, the use efficiency of hydrogen peroxide is about 89% to 90%. The use efficiency of hydrogen peroxide cannot be improved for lowering the production cost.
U.S. Pat. No. 5,290,533 and EP226258 disclose a method for preparing a titanium-silicalite molecular sieve having a transition metal, wherein the iron source is treated with ammonia to form the hydroxide precipitation, the hydroxide precipitation is washed, neutralized, dissolved in the template agent, mixed with the titanium-silicon solution, and then heated to form the molecular sieve. Such method is complicated.
Hence, the present invention provides a method for simplifying the preparation of the molecular sieve and a method using the molecular sieve of the invention for preparing cyclohexanone oxime which enhances the ammoximation of cyclohexanone and improves the usage efficiency of hydrogen peroxide.